1. Field of the Invention
The present invention relates to a pipe coupling. Particularly, the present invention relates to a pipe coupling for increasing the tightening force of a first half member and a second half member.
2. Description of the Related Art
A grooved piping system joins two pipes to be sealed without the welding process, and has been used in general buildings, power plants, industrial plants, water supplies, equipment piping, and air-conditioning piping systems.
Since the grooved piping system can join pipes without welding, the working time and costs are greatly reduced, and thus the system has been used for various fields of piping processes.
The grooved piping system comprises a gasket attached to the surface of pipes, and a pipe coupling disposed on the outside of the gasket to exert pressure thereto. The pipe coupling is composed of two half members having an identical shape.
Two grooves each are formed on outer surfaces of the ends of pipes joined to each other, and then the gasket is disposed between the two grooves. And, the pipe-joining process is completed by tightening the two half members of the pipe coupling which cover the gasket, by using a tightening means.
General structure of the pipe coupling having this function is described below.
FIG. 1 is a perspective view of a pipe coupling according to the related art, and shows the first half member 11 and the second half member 12 which are engaged with each other.
As mentioned above, the pipe coupling 10 is composed of a first half member 11 and a second half member 12, each of which is half-ring shaped. Flanges 11a and 12a having connecting holes 11b and 12b, are disposed on both ends of each of the half members 11 and 12.
Also, a pair of protrusions 11c and 12c with predetermined height are disposed on both sides of an inner surface of each of the half members 11 and 12. The protrusions 11c and 12c are received in the grooves disposed on the outer surfaces of the pipes during the pipe-joining process.
The ends of the first half member 11 and the second half member 12 have inclined surfaces 11d and 12d which are inclined over the widthwise direction of the half members 11 and 12 (i.e. the longitudinal direction of the pipe). Here, the inclined surface lid of the first half member 11 slidably contacts the inclined surface 12d of the second half member 12 corresponding thereto. Therefore, as the first and second half members 11 and 12 are met and tightened to each other, they slide on each other, thereby tightly joining the pipes.
When the two pipes meet each other, the gasket is disposed to cover the outer surfaces of the ends of the pipes. Then, the first and second half members 11 and 12 are disposed to correspond to each other, with covering the gasket.
In order to join the first half member 11 and the second half member 12, bolt 19 and nut 18 can be used as the tightening means. As the bolt 19 is inserted into the connecting holes 11b and 12b disposed on the flanges 11a and 12a, and tightened by the nut 18, the first half member 11 and the second half member 12 tighten the pipes, with sliding along the inclined surfaces 11d and 12d. 
By tightening the first and second half members 11 and 12, the gasket disposed inside the first and second half members 11 and 12 is compressed. Consequently, the two pipes are joined and sealed by the gasket and the pipe coupling 10.
Here, the contacting surfaces of the first and second half members 11 and 12 are the inclined planes 11d and 12d, and so the tightening force is exerted into the inclined direction (i.e. the arrow direction in FIG. 1). Also, the inclined direction of each of the half members 11 and 12 is opposite at both ends, and the direction of the tightening force is also opposite to each other. Therefore, the twisting force is generated by the pipe coupling 10.
In case the pressure of the pipes is rapidly increased, the protrusions 11c and 12c of the first and second half members 11 and 12 may be easily separated from the grooves of the pipes by the twisting force, which weakens the pipe-sealing ability of the gasket. Also, the twisting force exerted onto the first and second half members 11 and 12 is transferred to the gasket, to weaken the pipe-sealing ability of the gasket.